In een overzichtsartikel schetst Michael van den Heuvel de hindernissen bij het stellen
van de diagnose van de ziekte van Lyme /
het opsporen van Borrelia burgfdori-infecties.
Eén van de belangrijkste hindernissen is de (gebruikte) laboratoriumtechniek:
Daarnaast zijn er talloze variaties die het opsporen van infecties bemoeilijken:
- t.a.v. de (nieuw ontdekte) subsoorten van Borellia burgdorferi,
- t.a.v. het onderzochte monster (bloed, weefsel etc.), en
- t.a.v. het moment waarop een patient onderzicht wordt
(nieuwe infecties!).
Een belangrijke observatie betreft voorts de diagnose van de ziekte van Lyme/tekenbeet:
de kenmerkende huiduitslag, erythema migrans,
treedt niet bij alle patienten op (70-80%?).
Lyme Disease: Rolling the dice with ELISA
4. June 2013
In the clinic and the laboratory a war of a special kind is brewing.
Ticks transmit Borrelia burgdorferi
to 200,000 people each year, year in year out; a vaccine does not exist.
Tests have rather big shortcomings – and so some infection remains undetected for years.
....
Myths and Misconceptions:
....
John J. Halperin, Phillip Baker and Gary P. Wormser as part of
a review article criticised the fact that
doctors tend to base too much of their diagnosis on the respective characteristics on the skin.
The fact is that up to 50 percent of patients do not develop redness.
....
Now scientists have shown by using genetic analysis that
– in a process completely separate from the ailment already undergoing treatment –
a new infection of Borrelia is the cause.
Much Trouble with Antibodies
In suspicious cases specialised laboratories will analyse a blood sample using
enzyme-linked immunosorbent assays (ELISA) for antibodies.
The method has several drawbacks: sensitivity, specificity and standardisation do not meet expectations.
According to Dr. Armin Schwarzbach from the Borreliose Centrum Augsburg
up to 70 percent of all ELISA tests turn out negative despite presence of infection.
"The problem is that in the ELISA tests too few recombinant antigens and lysates are used in what are either wrong or incomplete blends.
We now know that there are numerous new Borrelia subspecies", says Schwarzenbach.
The pronounced antigenic variability and variation between individual subspecies is problematic.
....
Standards? Forget it!
....
"Immunoblots are indeed more sensitive than ELISA tests
but do not exclude possible presence of infection.
The GKV (association of obligatory health insurance providers) however
only refunds for the "dice game" being played with ELISA and
therefore leaves the fate of the patient in the hands of the manufacturers employed", the researcher criticises.
Immunoblots themselves achieve only 60 percent sensitivity.
....
News from the Lab
In addition to ELISA and immunoblots, methodologically sophisticated
lymphocyte transformation tests (LTT) have been established.
Laboratories isolate lymphocytes from a blood sample and
determining the extent to which a response to specific antigens then follows.
"I think the test is helpful, but is equally neither exclusive nor conclusive", says Schwarzenbach.
There remains the possibility of tracing bacterial genome in aspirates, tissue samples or biopsies via
a polymerase chain reaction (PCR).
A negative result does not necessarily also mean that patients are Borrelia-free.
....
Article by Michael van den Heuvel
http://news.doccheck.com/en/newsletter/92/636
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